Outdoor electronic devices must withstand outdoor environment, and thus be waterproof. Presskeys or buttons of electronic devices are generally installed in a limited space and move to input characters or commands, that waterproofing is made more difficult. FIG. 1 shows a waterproof presskey structure which includes a shell 100, a presskey 200, a silicone element 300, and a switch 400. The presskey 200 includes a key cap 201 and a post 202. A shoulder 203 extends from the key cap 201 and surrounds the key cap 201. The shoulder 203 is received in a slot 101 defined in the shell 100 and movable in the slot 101 along the direction of pressing/releasing the presskey 200. A width of the slot 101 along the direction of pressing/releasing the presskey 200 defines a maximum distance of travel, that is, the presskey 200 being pressed down or springing back up. The silicone member 300 is shaped as a hat and includes a body 302 and a flange 301. The body 302 is received in a through hole 102 defined in the shell 100 and receives the post 202 which has an end abutting against the bottom of the body 302. The flange 301 is stuck to the shell 100 using glue, to assemble the silicone member 300 to the shell as well as prevent water ingress. The switch 400 is positioned under the body 302. When the presskey 200 is pressed down, the post 202 presses the bottom of the body 302, the body 302 thus stretches and triggers the switch 400. When the presskey 200 is released, the body 302 restores the presskey 200. However, repeated use leads to failure of the glue between the silicone member 300 and the shell 100. As a result, the silicone member 300 breaks away from the shell 100, the waterproof presskey structure fails and the presskey 200 may fail as well. Furthermore, the thin bottom of the silicone member 300 provides little or no protection for the switch 400 when the presskey 200 is impacted, for example, during an accident such as the mobile phone being dropped. The presskey 200 fails if the switch 400 splits away or is damaged during such accidents. Third, being made of soft material, precise relative positioning of the silicone member 300 is difficult to achieve for even sticking to the shell 100 when the shell 100 is being assembled, which reduces the quality and productivity of the waterproof presskey structure.